NONSPORE-FORMING BACTERIA 93 



bacteriolytic substance most readily found in old culture media. None 

 of these substances was enzymatic in nature. Schoental found that pyo- 

 cyanin had a strong bactericidal activity, but its high toxicity and insta- 

 bility made it unpromising for therapeutic purposes. The action of 

 ^-oxyphenazine against many bacteria made it comparable to the fla- 

 vinesj however, it was less toxic and non-irritant. The third antibacterial 

 substance had a marked lytic action on vibrios, being bactericidal in a 

 concentration of i : 1 0,000 and bacteriostatic in i : 100,000. 



No less extensive is the literature on the antagonistic action of the 

 fluorescent group of bacteria, first established by Garre (311) in 1887 

 and later by others (50, 246, 302, 326, 430-43^, 462, 524, 525, 6s 5, 

 827). Hettche and Vogel (407) described the inhibiting effect of 

 strains of this organism on the growth of various gram-negative and 

 gram-positive bacteria (Table 15). The active substance is thermo- 

 stable, dialyzes through a membrane, and passes through Seitz and 

 Berkfeld filters (525). It is said (407) to be soluble in chloroform. 

 Aerobic culture conditions are favorable to its accumulation. Members 

 of this chromogenic group of bacteria were also found to be able to 

 bring about the lysis of infusoria (123). Rahn (711) observed the 

 phenomenon of iso-antagonism, which is associated with the formation 

 of a thermolabile substance that does not pass through a filter. Certain 

 bacteria were found (228, 711) to be favored by their own metabolic 

 products, whereas others had an adverse effect j the products of the 

 first group were usually thermostable and nonfilterable, and the second 

 were thermolabile (at 60° to 100° C.) and were destroyed by light. 



5. marcescens is known to exert antagonistic effects against a number 

 of bacteria, including diphtheria, gonococci, anthrax (743, 764), and CI. 

 chauvoei (209), as well as fungi causing insect diseases (587). The for- 

 mation of antibiotic substances by this organism has been demonstrated 

 by various investigators. These substances are active not only in vitro 

 but also in vivo ( 743 ) . Their activity increases with the age of the cul- 

 ture. Their formation was believed not to be associated with the pro- 

 duction of the pigment by the organism. They were also of a nonlipoid 

 nature. Hettche (409), however, asserted that the bactericidal action 

 of Serratia is closely related to pigment production. The pigment was 

 extracted with alcohol and was found capable of dissolving dead gram- 



